If it interests you to skim the bibliographies of either, you will find many, many, many more reference sources to delve into at your leisure, but these are the ones to buy and cherish and lob at subordinates in a fit of typo-fueled passion. (Be sure to get the hardcover editions.)

Both dictionaries are also accessible online: Webster's New World College Dictionary can be found at YourDictionary.com, and Merriam-Webster's Collegiate Dictionary can be found at M-W.com. Even though you forget your own home phone number, make sure you memorize these URLs!